Add support for per-tool signing configuration, configuration saving + minor bug fixes

[psreverttoself]

This PR makes 2 major changes and 1 minor bugfix:

1. Adds support for configuring per-tool (i.e Repeater, Intruder, Proxy, etc.) signing. The most common usecase that inspired this functionality change is in situations where we would like to sign request made in Repeater with a profile, but not Sigv4 requests captured in the proxy. By default requests from all tools will be signed (if applicable).
2. Add support for saving settings/configurations on a per-project basis. This can be toggled in the UI, but is currently on by default. This closes Save extension settings into project file #42.
3. (Bugfix) Handles an edge case where the Test Profile Credentials button would not always end up using the most up to date values in the associate profile's TextBox fields. This happens since immediately clicking the button while the textfield has focus doesn't trigger the current focus listener callback to fire, since technically the texfield doesnt lose focus when another button is clicked.