Replace usage of accessors and use getters & setters instead

[florian-h05]

To disable Nashorn compatibility mode, we need to replace usage of accessors on Java objects and use getters and setters instead.

We have to check and fix all files:

• [x] items/metadata/itemchannellink
• [x] items/metadata/metadata
• [x] items/item-history
• [x] items/item-sematics
• [x] items/items
• [x] rules/rules (rule builder relies on the JSRule)
• [x] actions
• [x] cache
• [x] log
• [x] osgi
• [x] quantity
• [x] things
• [x] time
• [x] triggers
• [x] utils