Custom scripts: allow to specify dynamic parameters

[gruberroland]

The script definition for manual scripts should allow parameters like LAM_SELECTION_1="dev,qa,prod". LAM_SELECTION_1 will then be resolved as wildcard to the script command ("$LAM_SELECTION_1$").
Users will see a drop-down list on the screen where manual scripts can be executed. Here, they can select the value for each parameter.

The LAM_SELECTION_1 definition should be on a separate line in textarea so it can be used in multiple scripts.

In addition, text boxes should be definable with LAM_TEXT_...

LAM_SELECTION_1:Some label=dev,qa,prod

LAM_TEXT_1:Some label=12345