Capitalize usage message and some user visible output

[bcr]

Summary

Some outputs form bectl (i.e. activating a BE) shows a message that starts with a lowercase character.
I think it would be better if those would start with uppercase.

Test Plan

1. Apply the patch
2. Recompile bectl.c
3. Check the output for the changed strings (i.e. when activating a new boot environment)

[bcr]

ping?

[imp]

Looks good to me