[WIP] Port to KDevelop 5

[z3ntu]

There are still many TODOs such as:

• [ ] Fix the isValid function as it returns true for some files (why?)
• [ ] Implement a GUI for KERN_VALIDFILES
• [ ] Change the display name for the options panel (ProjectConfigPage::name())
• [ ] Fix crashes (maybe they are just because at runtime the .so was replaced)
• [ ] Understand what some methods in the main plugin file do (and fix them if needed) e.g. the makefile parse method
• [ ] Adjust readme