sge: call _setup_sge_profile from within _inst_sge

The SGE profile setup is really part of installing SGE and belongs
within SGEPlugin._inst_sge
sge: remove redundant admin/submit host setup

All nodes are automatically added as submit and admin hosts by the SGE
installer script on initial cluster setup. Only newly added nodes (ie
from addnode) need to be explicitly added as submit and admin hosts.
sge: run qconf commands on exec host in _inst_sge

This avoids a threadpool issue where the same SSH connection object
can't be called by more than one thread. Each node in the cluster is an
admin host by default so the same qconf commands in _inst_sge can be
directly executed on the node being added as an exec host which avoids
the threadpool issue.
sge: fix parallel environment slot allocation

Updated the pe creation code to respect master_is_exec_host and
slots_per_host settings when computing the total number of slots for the
parallel environment.
addnode: fix help text
docs: convert github issue references to links
bump version to 0.95.4
update Changelog for 0.95.4 release
Merge branch 'hotfix-0.95.4' into develop