Vala and Meson compilation controls

## Problem

Right now the official method of making elementary apps is via the native code editor, so there might as well be an easy way to compile elementary apps.

## Proposal

Add cool controls to start a compilation script with meson, maybe even with integrated features specifically for target flatpak runtimes, archs and other useful app-making stuff.

## Prior Art

elementary-ide used to have this:
Panic's sexy code editor: