Rename doc to getting-started for introductory docs

Signed-off-by: Pavlos Ratis <dastergon@gentoo.org>
enrich docs with more introductory notes

Signed-off-by: Pavlos Ratis <dastergon@gentoo.org>
slight improvements to README

Signed-off-by: Pavlos Ratis <dastergon@gentoo.org>
remove project name header from readme
remove extra whitespace
use symlinked doc for duplicated info

The getting-started doc was basically a duplicate of the readme, so just
use that directly.
doc: use apostrophes in appropriate possessive places
doc: more readme tweaks

Mostly pointing to readthedocs instead of the dying/soon to be dead
pkgcore.org docs site. Note that we need to fix API and man page doc
generation for readthedocs, this will probably take reworking the build
a bit and perhaps adding a requirements.txt file so readthedocs knows
what dependencies are necessary for building docs.
doc: use separate links for the readme and rewrap lines
doc: update git repo and homepage
doc: minor repetitive simplification
use find regex to be a bit more strict about rejecting EAPI libs

Some point in the future we might have multiple digit EAPIs if the world
doesn't end first.
sort ebuild incrementals and metadata keys
minor spelling fixes
minor comment grammar fix
test: remove old <python2.6 compat
fix stable forced use flag formatting

Previously we weren't using the package.use.stable.force or
use.stable.force (and similar mask files) settings for displaying pkg
changes in the case where they should be used (merging stable pkgs with
only stable arches in ACCEPT_KEYWORDS).
properly filter injected phase functions from env

Previously they weren't getting filtered with the new dynamic EAPI
function filter method since the required functions are in common.lib
which wasn't sourced to avoid pulling all its other functions into the
env dump.

Now we source common.lib and then unset all its functions before
requesting the list of EAPI specific functions.
explicitly unset functions for bash

By default, unset called with no arguments will remove only the variable
matching the argument given if both variable and function exist with the
same name. Therefore, we'll be explicit when trying to remove function
definitions from the namespace.
pmerge: always generate the package new use restrict list

In the case where no atoms are passed it'll generate an empty
OrRestriction which should work as expected.

Fixes #13.