New variable to allow user to enable/disable prompts on starting REPL

[vlatkoB]

• Added haskell-process-load-or-reload-p variable with default value t meaning "do make prompt", so current flow is not changed unless user changes the variable to nil.
• Three functions changed just to check for haskell-process-load-or-reload-p variable and, depending on its value, make a prompt or accept the default:
  haskell-session-new-assume-from-cabal

haskell-utils-read-directory-name

haskell-session-target

[gracjan]

@vlatkoB: Almost great!

This should be defcustom.

Also make the default to NOT PROMPT. You will make a lot people happy that way. Okay?

[vlatkoB]

Done.
Travis fails because haskell-sort-imports.el changed in the mean time. Should you fix that, or should I?

[gracjan]

Already fixed. Please rebase on top of current master and push again.

[gracjan]

Thanks!