This is a board file format change to account for the new properties.
Also, we now only store the critical information about the dimension's
geometry in the board, rather than storing every drawn line.
The DIMENSION object is now an abstract base, and ALIGNED_DIMENSION
is the implementation that exists today (we will add more dimension
types in the future)
This makes the pcbnew multiline text editor natively accept tabs in the
same manner as eeschema and extracts key handling routines to the shim
to allow undo/redo.
Also allows Ctrl-Y under Linux in addition to other platforms. While
not as popular as Ctrl-Shift-Z, it is utilized for Redo in some contexts
While we're re-using the Text Properties dialog, it really covers all
properties for a Dimension, so it needs to be more clear what's text
and what's not. This changelist uses the Tooltips to store the more
explicit labels so they can still be edited in FormBuilder.