Merge pull request #53 from fqqb/master

Backport stable changes to master branch
very minor improvement
renamed system variables to system parameters and implemented a few of them in the TCP Tm Provider
typo
fixed the OnPeriodicRate
added a few utility functions for getting current instance and channel
small NPE fixes
cleanup old DaSS PP classes (moved to the yamcs-dass in svn)
make the list of parameters and containers in SpaceSystem and XtceDB sorted
very minor improvement
renamed system variables to system parameters and implemented a few of them in the TCP Tm Provider
typo
fixed the OnPeriodicRate
added a few utility functions for getting current instance and channel
small NPE fixes
cleanup old DaSS PP classes (moved to the yamcs-dass in svn)
make the list of parameters and containers in SpaceSystem and XtceDB sorted
simplify HornetqPpProvider and allow it to work with system parameters as well
simplify HornetqPpProvider and allow it to work with system parameters as well
Fix compile error due to changed api
Yamcs v0.26.4
Prepare 0.26.5 builds
Merge branch 'stable'