BApplication(const char *signature)
case 1:	signature is NULL =>
		Should print error message and quit.
case 2:	signature is no valid MIME string =>
		Should print error message and quit.
case 3:	signature is a valid MIME string, but doesn't have the "application"
		supertype =>
		Should print error message and quit.
case 4:	signature is a valid MIME string with "application" supertype,
		but a different one than in the app attributes/resources =>
		Should print warning message and continue.
		InitCheck() should return B_OK.
case 5:	signature is a valid MIME string with "application" supertype,
		and the same as in the app attributes/resources =>
		Shouldn't print anything at all and continue.
		InitCheck() should return B_OK.

BApplication(const char *signature, status_t *error)
cases similar to those of BApplication(const char *), if error is NULL,
otherwise error is set to the same value as returned by InitCheck()


