ClearScrollRequest should set a type parameter

Since ActionRequest requires a bounded type parameter.
[DOCS] various docs fixes

Removed unused misc.asciidoc file
Added plugins directory to directory layout
Fixed transport.tcp.connect_timeout value to match the code found in NetworkService.TcpSettings
Clarified that phrase query does not preserve order of terms
Clarified merge page
Added instructions on how to build documentation to docs/README
Mark 'lucene-expression' as 'provided' in pom.xml

We currently pull in the lucene-expression module that is referenced
by lucene-suggest. Yet, we don't make use of this dependency at all
and it pulls in a bunch of unshaded libs like `antlr` and `asm` which
are pretty common in other projects. We should exclude this
dependency since we don't use it at all and it causes problems
when Elasticsearch is used as a node client. (see #4858)

If we mark the dependency as provided it won't be included in the
distribution.

Closes #4859
Closes #4858