MetaTrader 5 build 2875: Improvements and fixes

Terminal

1. Fixed a bug which caused updated MQL5 standard programs to be copied to the terminal's root data directory instead of the MQL5 subdirectory. Due to this error, additional "Experts", "Images", "Include" and other folders could be created under the data directory.
   
   After the platform update, these folders will be checked and automatically deleted.
   
   
2. Fixed an error which used to prevent users from logging into the built-in MQL5.community chat.

Tester

1. Fixed optimization of Expert Advisors via the MQL5 Cloud Network. The optimization could fail to start under certain conditions.

MetaEditor

1. Fixed errors and crashes during MQL5 program debugging and profiling.

Updated documentation.