add "sync pending" notice and more pretty urls

* "sync pending" notice appears initially in place of project management buttons
* project management buttons replace "sync pending" notice after worker syncs
* added pretty_project_edit_path and pretty_project_decide_tip_amounts_path
      to ProjectHelper mostly to satisfy the new generalized "I visit ..." test paths
      but also helps the app url scheme be more consistent
* refactored ProjectsController#show action
* refactored bitcoin address update procedure to split long lines
      and abstract some magic numbers into config/initializers/constants.rb
* moved bitcoin address update procedure into Project#update_bitcoin_address
* defined blochain url constants in the CONFIG hash