Add -x and -s parameters to uploadexec

Added -x parameter to the script which indicates that the underlying
meterpreter session should be terminated when the execution has
finished.

Added -s parameter which takes a floating point number as an arg
which indicates the number of seconds to sleep between uploading
and executing. This helps in the case where http(s) payloads are
used for meterpreter and a time delay is needed to make sure that
the file has been written to disk and the lock released prior to
attempting to executing it.
Add the getenv command which pulls env vars from the victim

This command will allow the attacker to grab environment variables from the
target, if they exist. Calling this function allows for one or more values
to be passed in, which should match the name of the variable required. If
the variable is found, it is returned. If it is not found, the variable
is not returned (ie. it's not present in the resulting hash).

Note 1: POSIX environment vars are case-senstive, whereas Windows is not.
Note 2: POSIX doesn't seem to cough up user environment vars, it only returns
system vars. I'm not sure why this is, but it could be because of the way
we do linking on POSIX.
Fix title
Fix indendation on Gemfile
Land #2692, fix title for ms13_022
Fix nokogiri typo

[SeeRM #8730]
Land #2693 - case sensitive
Land #2694, indentation fixes for Gemfile
Use Rex.sleep instead of sleep
Land #2673, -x and -s for uploadexec meterp script
Add getenv support to python meterpreter

This change adds support for `getenv` to python meterpreter. Nothing too
complex going on here. I tidied up the definitions of the TLVs as well
so that they look nice.
Add PHP side for meterpreter getenv
Merge branch 'egypt/feature/getenv-php' into getenv_cmd
Land #2689, getenv