Added test for chart title rotation.
Fix for Pie chart lengend fonts.
Added delete_series to Pie chart legends.
Added test for Pie chart legend overlay.
Added interval unit for categoty axes.
Prep for release 0.75.
Merge commit 'CPAN_0.75'

Conflicts:
	lib/Excel/Writer/XLSX/Chart.pm

This version includes additional functionality that is tested through
the t/regression/experimental*.t files as follows:

01 -> y2 support (Now part of 0.51+)
02 -> title font support name_font (Now part of 0.53+)
03 -> legend font support (Now part of 0.73+)
04 -> legend layout support (now part of 0.74+)
05 -> axis tick label skip support (now part of 0.75+)
06 -> axis tick mark skip support
07 -> axis number format support num_format (Now part of 0.54+)
08 -> axis label rotation (Now part of 0.69+)
09 -> axis label font num_font (Now part of 0.53+)
10 -> axis title font name_font (Now part of 0.53+)
11 -> axis title rotation (Now part of 0.69+)

Item 4 requires mapping w -> width and h -> height
Item 5 requires mapping tick_lbl_skip -> interval_unit
Item 8 requires mapping num_rotataion -> num_font{rotation}
Item 11 requires mapping name_rotation -> name_font{rotation}