Implement slime blocks pushing and proper handling of non-movable blocks by pistons

[Red-Teapot]

Added PistonMoveBehavior enum and corresponding methods in MaterialValueManager to store information about blocks push/pull behavior (e.g. bedrock does not push and pull, flowers drop when pushed and can't be pulled). All blocks can be pushed and pulled by default.

Pistons (including sticky variant) handle the behavior.

I haven't filled materialValues.yml yet so only bedrock and cobweb work for now.

[Red-Teapot]

I think I've fixed all the stuff I needed to fix. Material push/pull behaviors are not filled yet though. Works only for cobweb and bedrock just as an example of non-pushable/drop-on-move blocks.

[aramperes]

This logic doesn't take into account stuff like the doTileDrops gamerule and breaking containers (dropping chest contents). This kind of logic is already implemented in the DiggingMessage handler. Could you somehow merge this code?

If not, please leave a TODO and open an issue to support this.

[Pr0methean]

What are the correct piston behaviors for water and lava? Also, do we need special handling for blocks that can fall after being pushed (sand, gravel, concrete powder, dragon egg)?

[mastercoms]

Merging this because it's a great start in our incomplete server implementation. Will iterate further based on reviews in this PR.

[Red-Teapot]

@Pr0methean Movement behaviors for liquids are specified in material values. The only difference is that getMinedDrops() for liquids returns item stack containing liquid block (the method is not overridden). I'm not sure if I should override that method to return an empty stack so I made a workaround. It seems like liquids are destroyed on push and do not move on pull in vanilla game.

Regarding gravity-affected stuff, it's hard to say because it is hardly working already, e.g. blocks don't fall when a block below them is destroyed. Maybe I'll try to find out how to make blocks fall when I get some free time.