Add Environment variables

[vindevoy]

Add environment variables that can be used in Linux or MacOS for determining the directories used by CherryBlog

Solution:

• Add CHERRYBLOG_HOME
• Add CHERRYBLOG_DATA
• Add CHERRYBLOG_THEME
• Add CHERRYBLOG_VAR
• Add CHERRYBLOG_RUN

[vindevoy]

Goes to the backlog again to finalise the 1.4.0 (SSL)