Feature/early eval for parameterized options

[ppcamp]

Description of changes:

Add support to early eval an option item.

# same as used to be
cat <file=$(ls)>

# same as used to be
cat <file=|__|_$(ls)_|>

# same as used to be
cat <file=|_opt1_|_opt2_|>

# ADDED
cat <file=|_$(ls)_|>

In this case (last scenario), it'll execute ls using cmd/runner/Run function (which keeps record of folder and shell to use), before create the gui, therefore, allowing user to just select one of the output elements.

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