v2021-rc.1

• remove topology item (#486)
• switch to local includes (#487)
• add default units to readers (#483)
• update bead related classes (#475, #474, #469, #468, #460)
• update boundary class (#457)
• fix usage of PROJECT_SOURCE_DIR in cmake (#517)
• document cmake options and packages (#520)
• drop WITH_GMX in cmake in favor of auto-detect (#523)
• standardising include order and style in header files (#531)
• make scripts always executable in builddir (#533, #550, #556)
• rename REGRESSIONTEST_TOLERANCE to INTEGRATIONTEST_TOLERANCE (#534)
• standardising include order and style in library files (#542)
• move CI to GitHub Ations (#551, #552, #553, #561, #562, #593, #617,
  #632)
• format CMake internal cpp code (#557)
• update codacy badge (#558)
• convert markdown to rst format (#559)
• read units stored in H5MD file (#549)
• enable CXX only in CMake (#560)
• refactored tests to use files instead of data in source code (#572)
• corrected max index in csg_resample (#575)
• add periodic extrapolation for dihedrals (#576)
• bump required CMake version to 3.12 (#599)
• Fixed boost test deprecation warnings (#598)
• improve error message for broken binaries (#601)
• Fixed memory leaks in tests and neighbourlist (#602)
• format with clang-11 (#604)
• use unique_ptr in factory (#603)
• Convert remaining md files to rst (#616)
• merge csg-manual (#621, #622)
• merge in csgapps repo (#623)
• Pdbs with more than 10000 resids can now be written (#627)