add common crate

Signed-off-by: xermicus <cyrill@parity.io>

crates/common/src/base.rs

@@ -0,0 +1,15 @@
+//!
+//! The number base constants.
+//!
+
+/// The binary number base.
+pub const BASE_BINARY: u32 = 2;
+
+/// The octal number base.
+pub const BASE_OCTAL: u32 = 8;
+
+/// The decimal number base.
+pub const BASE_DECIMAL: u32 = 10;
+
+/// The hexadecimal number base.
+pub const BASE_HEXADECIMAL: u32 = 16;