AEM_CNTRL: Enhance aem_cntrl to support additional actions such as `start`, `stop`, and `waitfor`

Add additional actions to the aem_cntrl utility, such as:

`start` - This will start AEM and wait for it to be up before returning. This is useful when to automate the launching of AEM before deploying files to is from script.

`stop` - This will stop AEM and wait for it to shutdown before returning. This is useful when automating the shutdown of AEM before starting it again.

`waitfor` - Wait for a line in the log that matches the regular expression provided. This is useful for scripts that want to wait until a certain event happens (e.g. a bundle is installed, or package is finished installing).

Sub-issues to this issue will be created for the implementation of each command.