Limit images sizes and make more uniform (LaTeX)

This patch adjusts some problems regarding image sizes in LaTeX output of doxygen (a.o. Bug 738299 - When using msc or PlantUML, the default latex for the created image should include [width=\linewidth]) this has been done is such a way that all the "image" commands (i.e. image, dot, dotfile, msc, mscfile, diafile, startuml) operate in a similar way / have the same possibilities.

- commands.doc
Adjusted documentation to reflect changes.

- cmdmapper.cpp
- cmdmapper.h
Added utility function to map command id back to command name

- doctokenizer.h
- doctokenizer.l
Handle Caption  and Size indication. Required also that some other rules had to be tightened a bit (like usage of {} in startuml and usage of "" for captions. This was already described in the documentation in this way).

- docparser.cpp
- docparser.h
Created routine to uniformly handle the Caption and size indications and store them in a general way.

- latexgen.cpp
Replaced graphicx package by adjustbox package (includes graphicx) to support "min width" etc.

- doxygen.sty templates\latex
Added commands to make commands with and without caption behave similar.

- docbookvisitor.cpp
- docbookvisitor.h
- htmldocvisitor.cpp
- latexdocvisitor.cpp
- latexdocvisitor.h
- printdocvisitor.h
- xmldocvisitor.cpp
Created routine to uniformly handle the Caption and size indications in a general way.

- indexpage.xml (testing\022)
- indexpage.xml (testing\031)
- class_receiver.xml (testing\037)
- class_sender.xml (testing\037)
Adjusted example output.
Merge branch 'feature/bug_size_latex' of https://github.com/albert-github/doxygen into albert-github-feature/bug_size_latex

Conflicts:
	src/doctokenizer.h
	src/latexgen.cpp
various fixes and restructuring
Merge branch 'master' of github.com:doxygen/doxygen