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
Bug 741778 - \cite confused by labels ending with a dot (improved warning message)
Remove redundant code
Disabled enter/exit printing for doctokenizer (produced too much noise)
Fix to ignore the contents of \verbatim and friends while looking for sections
Bug 739210 - C++11 scoped enums with same name inside different classes are merged if using tagfile
Show tag file name instead of <unknown> for warnings pointing to symbols extracted from tag files.
Bug 739209 - Invalid warning about undocumented C++ function imported from tagfile
Bug 737830 - Invalid element name in footer part when GENERATE_TREEVIEW specified
Bug 739462 - Using "doxygen.css" for HTML_EXTRA_STYLESHEET fails silently
Bug 738173 - Entity references in XML code command are incorrectly handled
Bug 729063 - Missing link for item inside the same namespace
Bug 741100 - Latex to PDF hangs when using Markdown tables
Bug 685597 - C# <code> tag in an <example> tag does not render as expected.