Pdfcropmargins

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New features:

* The GUI layout has been rearranged for more intuitive use of the options that take
four values, one for the left, bottom, right, and top margins.

* The GUI now displays the minimum cropping delta values as buttons which take you
to that page. This is helpful for fine-tuning cropping without cropping-out useful
information.

* Page numbers and uniformOrderstat widgets in the GUI were changed to spinners.

Bug fixes and maintenance:

* Internally, functions were renamed to match the recent PyPDF2 deprecations.

* Fixed bug caused by adding pdfcropmargins as an alias.

* Fixed bug when uniform mode not selected, and extend min delta display to both
cases.

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Bug fixes:

* Fixed a bug where a file with unreadable metadata can have a bad attribute access.

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Bug fixes:

* The precision of the cropped point values for the new margins is now limited (to 8 after
the decimal) to avoid possible problems with some PDF viewers.

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Bug fixes:

* Pinned PyPDF2 version to < 3.0.0 because of breaking changes.

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New features:

* Added the new ``--cropSafeMin4`` (``-csm4``) option to specify a safe minimum
margin other than the bounding box.

* The two new options ``--keepHorizCenter`` (``-khc``) and ``--keepVertCenter``
(``-kvc``) have been added. These options ensure that the respective
relative horizontal and vertical centers of pages remain the same (by
cropping the minimum of the two delta values on each page).

Bug fixes:

* Save previous state for uniform checkbox to restore after being implied/disabled.

* Get cropSafe working more correctly with page ranges.

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New features:

* Implement the new ``--cropSafe`` (``-cs``) option which ensures safe crops if
enabled.

Bug fixes:

* Workaround for a bug in the GUI uniform button.