Initial version of bfCheckJavaMemory

This displays a warning message if the heap space is below 512m.  Only
functions that call setId currently call bfCheckJavaMemory.
Update copyright year
Allow the minimum memory value to be specified

The default value is still 512m.
bfCheckJavaMemory: fix typo in function definition
bfCheckJavaMemory: use 'warning' instead of 'fprintf' for logging
Change warning ID from 'bf' to 'BF:lowJavaMemory'

...as suggested by @sbesson.
Add unit test class for bfCheckJavaMemmory() function
Combine warning messages to have one warning with specified ID
Merge pull request #11 from sbesson/matlab-memory

Unit test for bfCheckJavaMemory
Merge pull request #856 from melissalinkert/matlab-memory

Initial version of bfCheckJavaMemory