CD matrix now updated, if present, when Map pixel size is changed.
Better pattern for checking for key existence in dictionaries
Merge pull request #1187 from ayshih/resample

CD matrix now updated, if present, when Map pixel size is changed.
Fix PC matrix calculation from CD matrix.

This fixes a bug with SWAP files.
Write some broken tests.
Fix CD matrix test and test file
fix database test numbers
Conflicts:
	sunpy/database/tests/test_tables.py