removed boost and petsc build from gitlab-ci

.gitlab-ci.yml

 ---
-cache:
-  paths:
-  - install/boost
-  - install/petsc
-
-before_script:
-  - tools/install_boost.sh
+image: mathiwr/amdis-base:debian9
 
 build:9-debug-gcc:
   stage: build
-  image: duneci/base:9
   script:
   - tools/build_amdis.sh Debug
   only:
@@ -17,7 +10,6 @@ build:9-debug-gcc:
 
 build:9-release-gcc:
   stage: build
-  image: duneci/base:9
   script:
   - tools/build_amdis.sh Release
   only:
@@ -25,18 +17,14 @@ build:9-release-gcc:
 
 build:9-parallel-debug-gcc:
   stage: build
-  image: duneci/base:9
   script:
-  - tools/install_petsc.sh
   - tools/build_parallel_amdis.sh Debug
   only:
   - master
 
 build:9-parallel-release-gcc:
   stage: build
-  image: duneci/base:9
   script:
-  - tools/install_petsc.sh
   - tools/build_parallel_amdis.sh Release
   only:
   - master