Bug fix for scm/force-update, add general/manually task, bug fix for symfony2/doctrine-migrate, improve symfony2/cache-clear

Update "scm/force-update":

Change runCommandRemote() to runCommand(), you decide if the command is running local or remote depending of the stage you put the scm/force-update task. Remove the last $result =$this->runCommandLocal($command), it is not necessary.

Add "general/manually":

The purpose of this task is to provide a way to run multiple custom commands for your specific project, before Magallanes will have build-in tasks for your needs. Also maybe you'll just not consider you should create custom tasks for all commands you need (e.g. specific user rights for specific files and directories).

Example of usage:
 
    - general/manually:
        - find . -type d -exec chmod 755 {} \;
        - find . -type f -exec chmod 644 {} \;
        - chmod +x bin/console
        - find var/logs -maxdepth 1 -type f -name '*.log' -exec chown apache:apache {} \;

Update "symfony2/doctrine-migrate":

The task class was renamed to "DoctrineMigrateTask" instead of "DoctrineMigrate" (which did not work and cause errors).

Improve "symfony2/cache-clear":

Add optional parameters for symfony2/cache-clear task like --no-warmup.

Example of usage: 

    symfony2/cache-clear: { env: dev, optional: --no-warmup }