Add custom group names for options

[scottaiton]

Add the ability for users to define custom names for option groups.

This is an api breaking change would require all apps to use the new signatures.

For example, the following clawpatch there the function

fclaw2d_clawpatch_options_t *
fclaw2d_clawpatch_options_register(fclaw_app_t* app, const char* configfile);

would change to

fclaw2d_clawpatch_options_t *
fclaw2d_clawpatch_options_register(fclaw_app_t* app, const char* name, const char* configfile);