add option to drop views during DropCommand

[torhoehn]

Magerun pull-request check-list:

• Pull request against develop branch (if not, just close and create a new one against it)
• README.md reflects changes (if any)
• phar fuctional test (in tests/phar-test.sh)

Summary: (some words as summary)

Fixes #602.

Changes proposed in this pull request:

• Extend the database helper to return views
• Adopt table drop logic also for views in db:drop command

[torhoehn]

just copied from getTables function, has to be tested and developed

[cmuench]

@torhoehn nice. I will review that after the next release if it's ok. Or we discuss it in Cologne :-)

[torhoehn]

@cmuench I'm sure you could teach me something there. :)

[cmuench]

@torhoehn I didn't forget your PR. I plan to merge this feature in the v7.0.0 release.

[cmuench]

@torhoehn I remove the "-v" shortcut. This produces an error, because the "-v" option is already reserved as global shortcut of the verbose option in Symfony Commands.
The I rebased the branch with latest develop branch of n98-magerun2 which got a bigger refactoring. Jobs are running. I will do further tests in the next days.

[cmuench]

I tested the drop function.
It's currently not working. I got this error SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual th at corresponds to your MariaDB server version for the right syntax to use near 'LIKE 'view%'' at line 1

The generated SQL query looks like this:
SELECT table_name FROM information_schema.views WHERE table_schema = database() AND LIKE 'view%';

I left the "echo" statement in the code for debugging.

[cmuench]

I close this MR until we have refactored the command.