Display warning message if module to load/unload is already loaded/unloaded

[xdelaruelle]

As described by @mcytu, it would be nice to get a warning message when a module unload does not unload anything because the specified module is not loaded.

Following the same trend, it would also be nice to get this kind of warning when a module load does not load anything as specified module is already loaded.

The idea here is to add a ./configure option, a MODULES_ environment variable and a command-line switch for load, unload and switch commands to control whether or not a warning message should be printed if a module to load or unload is already loaded or unloaded

[wenzler]

Sorry, found another difference for non existing modules that might be considered related :)

v3
module rm bla
ERROR: Unable to locate a modulefile for 'bla'

v4
module rm bla
nothing - exit code is also 0

[xdelaruelle]

@wenzler I have just created a dedicated issue for this (#199). Precisely, v3 is silent whereas v4 returns an error when modulefile does not exist

[xdelaruelle]

Will report informational messages in case the verbosity level is verbose2 or any higher level.