Option to append plugin' name to the extra commands typed

[jfbourdon]

Adds a checkbox to automatically append the plugin's name to the command. That way, I can let a script manage the origin and destination of files based (copying from dev directory to QGIS plugin directory):

Currently, I have to type in the extra commands text box something like python C:\dev\copyMyPlugin.py pluginUnderDevelopment. With his PR, I only need to type python C:\dev\copyMyPlugin.py and the pluginUnderDevelopment will be appended as the last argument automatically. That way, if I now switch my development to coolOtherPlugin, I don't have to change anything in my command and risk messing things up by misspelling the name for example.

Second thoughs It may not be the best approach. I was also thinking of simply adding a function to replace a specific string like %PluginName% by the plugin's name everywhere in the command string. That way, the name can be used at multiple places instead of just at the end. I would be replacing extra_commands += " " + currentPlugin() by extra_commands = extra_commands.replace('%PluginName%', currentPlugin()). I think it would have the added benefit to be more explicit.

[jfbourdon]

I convinced myself, a search and replace approach is just better in every way.

[jfbourdon]

The search and replace could also always be performed. That way, there isn't a new checkbox:

[borysiasty]

@jfbourdon I'm sorry, I missed all the notifications from this repo somehow! I like the third solution the most. The simpler, the better :) Could you please push it to the PR?

[borysiasty]

@jfbourdon Forget it, it's just two lines so I'm just doing it. I'm closing this MR, but the change will be done.

[borysiasty]

Here it is (with some extra love to the gui, eg. now the TextEdit availability is controlled by the checkbox): 8a83b74d6514b