cw-mux fail gracefully in the absence of a topology diagram

Overview page now states the following:
Diagram not available for topology \"$TOPOLOGY\"

Ticket: CE-195
Testing Done: Tested on p2s
cw-mux topology diagram for p2s

Ticket: CE-195
Testing Done: Tested on p2s
cw-mux diagram for 2s6000

Ticket: CE-264
Testing Done: tested on 2s6000
cw-mux topology for 4810_1s

Ticket: CE-195
Testing Done: tested on 4810_1s
add inter switch links for cw-mux diagrams 2lt22s p2lt22s

Ticket: CE-245
Testing Done: none. change based on lab docs.
increment cw-mux version number

Ticket: CE-195,CE-245,CE-264
Merge pull request #8 from CumulusNetworks/cw_mux_ssh

cw-mux lab diagrams update