More variants for MFEM (#4533)

* fixes #967

* Version bump to 0.9.1

- Bugfixes for spack find
- 0.9.1 can read specs from current develop.

* Don't assume spack is in the path when building docs.

* adding mfem variants; do not assume build defaults

* adjusting format to clarify options

* fixing some build issues

* fixing mfem+sundials

* removing mesquite variant...turns out it is obsolete

* adding examples to mfem; fixing sundials darwin installs

* adding some additional variants and setting some configure flags by fiat

* switching most check_variants logic to conflicts() directives

* adding comment about cmake config

* fixing flake8 issues; thought I had already done that

* moving func def into install method

* switch yes_no to no_yes; fix miss-spelling of miniapps

* switching make target all to lib

* changing yes_no to function as requested; fix problem with same in sundials

* fix missing import sys directive

* adding master and develop versions to amrex

var/spack/repos/builtin/packages/amrex/package.py

@@ -33,8 +33,9 @@ class Amrex(CMakePackage):
     homepage = "https://ccse.lbl.gov/AMReX/index.html"
     url      = "https://github.com/AMReX-Codes/amrex.git"
 
-    version('develop', git='https://github.com/AMReX-Codes/amrex.git', tag='master')
     version('17.06', git='https://github.com/AMReX-Codes/amrex.git', commit='836d3c7')
+    version('master', git='https://github.com/AMReX-Codes/amrex.git', tag='master')
+    version('develop', git='https://github.com/AMReX-Codes/amrex.git', tag='develop')
 
     variant('dims',
         default='3',