Add description and dependencies to mod.conf

The legacy `depends.txt` and `description.txt` files are no longer
needed since Minetest 5.0.0 or later will read everything from
`mod.conf`.

This raises the minimum supported Minetest version to 5.0.0.

CHANGELOG.md

@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - `settingtypes.txt` file to allow configuring settings in the main menu.
 - Polish translation.
 
+### Changed
+
+- The minimum supported Minetest version is now 5.0.0.
+
 ## [1.3.0] - 2019-03-23
 
 ### Changed

depends.txt

@@ -1,6 +0,0 @@
-default
-intllib?
-stairs?
-farming?
-wool?
-basic_materials?

description.txt

@@ -1 +0,0 @@
-Adds various miscellaneous blocks to the game.

mod.conf

@@ -1 +1,4 @@
 name = moreblocks
+description = Adds various miscellaneous blocks to the game.
+depends = default
+optional_depends = intllib,stairs,farming,wool,basic_materials