Build system and CLI switch to request webinterface

Conflicts:
	pronterface.py

Refactor the README to make packaged binaries more obvious

Conflicts:
	pronterface.py

Patching the load command so that it works with the pronterface ui

Patching do_load so that it updates the pronterface ui when the load command is used within pronterface

Conflicts:

	pronterface.py

Fixes #271

The new algorithm mangles the request string as before,
but then looks for the first valid number instead of
a number in fixed places. This hopefully works for
all firmwares.

To avoid future regressions, a list of sample strings was
started. Feel free to add more samples in.

While neither PCB milling nor comments in parentheses are
part of the innermost core or RepRap printing, they happen
and should be handled gracefully.

Do not echo messages from printer twice when in loud mode

Add debug option to menu

As this is now part of the standard interface, it's pointless
to list it as possible extension code.

In a source code repository, all sources should be visible,
including those meant to be hidden at runtime.

In verbose mode (self.p.loud = True), the code actually sending
the G-code line prints this, too, so this was a duplicate.

Making these visible should help users to find out what's going
on on unexpected printer behaviour.

No new functionality.

Also remove the chdir() to pronterface.py directory

Also install webinterface deps and fix bug in configfile()

Factorize into a single function and support Marlin-style reports

fix custom button drag and drop being broken, with different strategy (1px size) to hide the drag-drop targets when not in use

Make crash in estimation code not block file load.
Diable web interface by default.