namespace: Extracted keyword finding logic to a separate class.

The idea of this refactoring was to split keyword finding logic away
from way too long and pretty horrible `Namespace` class.  The main
motivated was to ease adding new features (e.g. #888) and fixes
(e.g. #1771) to the keyword finding logic. New `KeywordStore` is still
too closely coupled with `Namespace`, but didn't want to do much
bigger changes in a minor release.

@guykisel, any comments about the changes are appreciated. It seems to
me that the approach I used was very similar to what you have done in
your fork to implement #1771.
atest: cleanup
Fixed using keyword with dot in name using long format.

For example, `MyLib.Keyword.with.dot` and also `My.Lib.Keyword.with.dot`
work now. Closes #1771.
Converted atest/README and utest/README to reST.

Both actually were (mostly) valid reST already so the biggest change
was renaming files to use `.rst` extension. The commit also contains
some fixes to syntax and small enhancements to docs.
atests: New functionality to verify expected errors using glob pattern.

Now expected error can be specified using `FAIL GLOB:` in addition to
`FAIL REGEXP:` and `FAIL STARTS:`. The motivation was to ease matching
more complex or changing errors without needing to use regexps.
Glob patterns are simpler and, most importantly, require less escaping.

Pull request #1776 provides a concrete use case for this functionality.
removed doc/examples/using_c that was already moved to https://bitbucket.org/robotframework/cdemo
Removed very old and really bad examples.

Demo projects linked from robotframework.org and examples in User
Guide and library docs are much better than these.
Removed outdated doc/java/. Currently Javadocs are under doc/api/_static/javadoc/.
typo fix. thanks @guykisel for spotting this.
Added tests for non-ASCII names with dynamic libraries
align docs correctly
Enhanced installation instructions.

Motivation is to make use these same instructions also as INSTALL.rst
in project root (#1779).

Changes done now:
- Drop references to One Click Installer (only worked on XP) and
  already removed non-standard install.py script (#1753).
- List using pip as the first and most recommended installation approach.
- General clean-up.
Removed info about libdoc etc. entry points from installation instructions.

These entry points are nevertheless explained in detail under the doc
of each tool. The goal is to simplify installation instructions as
discussed in #1779.
rename to .rst and add link
change to bullet points
remove useless colons
Merge pull request #1780 from laurentbristiel/master

change template/README.txt to .rst + use bullet points in the file
add missing space + explicit that when key exists then update is done
Merge pull request #1782 from laurentbristiel/master

add missing space + explicit that when key exists then update is done