Add GenericIndicator mini-widget to display generic data

[rafaellehmkuhl]

To start, it allows displaying data inside the genericVariables object, which is currently being populated by the NAMED_VALUE_FLOAT messages from Ardupilot.

Fix #410.

[patrickelectric]

There is a missing fixup commit in the middle of the PR, also, canso we add a background over each icon to make it more clear there you can click or choose one of them, like a button background or something, to give a bit more of contrast.

[rafaellehmkuhl]

There is a missing fixup commit in the middle of the PR, also, canso we add a background over each icon to make it more clear there you can click or choose one of them, like a button background or something, to give a bit more of contrast.

Will add some modification on hovering to tip on that.

[rafaellehmkuhl]

There is a missing fixup commit in the middle of the PR, also, canso we add a background over each icon to make it more clear there you can click or choose one of them, like a button background or something, to give a bit more of contrast.

Added modified bg color on hover for clarification.