checkplotserver: added object status placeholders for cplist
checkplotserver: added object status placeholders for cplist

the prefix tags will designate object status

* -> object has changed in project view from checkplot pickle
s -> object changes were written to the pickle

the postfix tags will designate object status in the checkplot list:

V -> object is variable
? -> object may be variable
X -> object is not variable


Former-commit-id: 0d917459059b607e7b81852b1192d42622d1ecdb
waqasbhatti/astrobase,lgbouma/astrobase,lgbouma/astrobase,waqasbhatti/astrobase,lgbouma/astrobase,waqasbhatti/astrobase