#899: Improve escaping options for core-exec: allow --escape=0 to disable argument escaping. Suppress shell escaping for shell aliases in the usual case, when arguements are provided as a string.
Disable escaping for shell aliases only if the shell alias begins with "!".  In this instance, the user is expected to pre-escape the shell alias for the shell (bash).  For other shell aliases, existing behavior is maintained.
Use all caps for boolean TRUE and FALSE.
Merge pull request #954 from greg-1-anderson/exec-escaping

#899: Improve escaping options for core-exec