Added config option to keep direction for free cells

[csnv]

Pull Request Prelude

• I have followed proper Hercules code styling.
• I have read and understood the contribution guidelines before making this PR.
• I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

Added configuration option keep_dir_free_cell. Although it is set to false, I would like it to be enabled by default in Hercules.
This option allows discovery of free cells based on the unit's current facing direction instead of always using EAST, which have the following advantages:

• Improves distribution of mobs when dispersing after being grouped. This setting allows monsters to spread in a circular fashion instead of forming a long horizontal line.
• Allows characters to move more naturally if they came from the east, instead of walking back.
• In some instances, fixes issue Unable to get item #1241 allowing the user to obtain the item.

This commit also fixes #1241 in all scenarios not allowing the character to enter a walk loop. Fix based on rAthena's.

Issues addressed:
#1241

[skyleo]

Love the idea!