Some small fixes for better user experience

1- "Play" - used in two different situation (start menu and demo menu) with same translation, but tjey have different meanings. It is a problem for some languages.  e.g. Brazilian Portuguese ;

2- Source had "Spactating", while translation file has "Spectating" correctly;

3- When capture the flag, a message is displayed without translation. Here is the fix for the source, but teeworlds-translation must be updated...