Avoids progress reporting arrow overlapping the line numbers.

Python reports line numbers based on the code context it has. These
can be wrong if the selection is part of a larger file. Padding the code
then allows the raw numbers being reported to be used.

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- Added more information of failure handling.

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- Added descriptive comment.
- Renamed parameters.

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- Extracted out a walk function.

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- Attempted to make BuildSubtreeItems more readable
  by adding methods.
- Removed unecessary depth parameter for buildRecursive.
- Initial insertion is now performed in the same branch as
  append was.
- Added a comment explaining the differences in the two depth variables.

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- Refactored ExtractSubtrees making the new API accept a
  std::vector<Row>.
- ExtractSubtrees nows validates preconditions before starting
  extraction, this is likely to have a perf impact but massively
  improves readability of the code.
- Moved subtree using alias into subtree header.
- Subtree header also contains common validation from FindSubtreeRoots
  and ExtractSubtrees, use of boost transform iterators allows us
  to share this logic without having to copy RowLocations from the
  vector of rows into a new vector.

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Caused by not updating the model index used to get the parent when
inserting children. A future commit should perform some refactoring
and add some comments.

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Some simple heuristics can be applied, we now do multiple separate
passes over the list of locations but the resultant class is now
stateless and much more readable.

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Both algorithms would return non-empty optionals for tree selections
where a subtree with a root at greater depth came before a subtree
with a root at a lesser depth. Such as

[0, 0]
[0, 0, 0]
[0, 0, 1]
[1]
[1, 0]
[1, 1]
[1, 2]

This should not be the case as the expected behaviour for these
cases is ambiguous.

This commit fixes this behaviour for both algorithms and adds
unit tests for the above case.

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- Tidied up fix in previous commit for tabbing over uneditable cells.
- Added guard to do nothing for calls to editAt for uneditable cells.
- Added code to close open editors when using setCellAt or setCellsAt
  to make cells uneditable.

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- Was causing an error on an older version of SIP.

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- Renamed signal and assosiated notification methods.
- Added old text as a signal parameter.

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Prior to this commit, copying a collapsed tree of nodes would result
in only the root node being copied. This PR changes that so that
selected expanded nodes with no selected decendants and unexpanded nodes
impliciltly include their decendants in the seleection.

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- Used index of inserted index to determine parent for recursive call
  rather than the index in the row location. When building alongside an
  existing subtree these indices may differ.
- Make BuildSubtreeItems store a copy of RowLocationAdapter.

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This vector.sip is now heavily modified from the original due to the
use of SIPVector.h

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