Memoizer: save current revision number in memo file

The memo file is then invalidated if the saved revision number does not
match the current revision number.  This required bumping the internal
memo file version number from 1 to 2.
Add method to disable revision checking

Calling 'setVersionChecking(true)' will disable revision checking, but
keep major/minor version checking.  This may be useful for cases where
doing strict revision checking would cause an inordinate amount of
overhead.
Use the PDF artifact in the release landing page
Remove superfluous HTML options in Bio-Formats landing page
Fix daily artifact link
Merge pull request #685 from sbesson/landingpagefix

Downloads page: use PDF artifact
Fix usage of tilde for Matlab versions earlier than R2009b
Drop typecasting workaround for Matlab versions earlier than 7.1
Add note about minimum supported version of MATLAB in the documentation
Add version note to the developers MATLAB page
Also capitalize MATLAB in the developers documentation page
Merge pull request #646 from melissalinkert/invalidate-cache

Save current revision number in memo file
Merge pull request #693 from sbesson/rebased/develop/matlab_versioncheck

Fix bfGetReader for MATLAB R2009a and earlier (rebased onto develop)