Improve resolution of relative includes (#489)

* Add aeso_utils:canonical_dir/1

* Add current file directory when resolving includes

* Add CHANGELOG

* Add documentation

* Add a test case

* Properly keep track of src_dir

test/aeso_compiler_tests.erl

@@ -161,6 +161,7 @@ compilable_contracts() ->
      "state_handling",
      "events",
      "include",
+     "relative_include",
      "basic_auth",
      "basic_auth_tx",
      "bitcoin_auth",

test/contracts/dir1/bar.aes

@@ -0,0 +1,4 @@
+include "../dir2/baz.aes"
+namespace D =
+  function g() = E.h()
+

test/contracts/dir2/baz.aes

@@ -0,0 +1,3 @@
+namespace E =
+  function h() = 42
+

test/contracts/relative_include.aes

@@ -0,0 +1,3 @@
+include "./dir1/bar.aes"
+contract C =
+  entrypoint f() = D.g()