[server] introduce default values

ivette/src/frama-c/kernel/api/ast/index.ts

ivette/src/frama-c/kernel/api/data/index.ts

ivette/src/frama-c/kernel/api/project/index.ts

ivette/src/frama-c/kernel/api/properties/index.ts

ivette/src/frama-c/kernel/api/services/index.ts

ivette/src/frama-c/plugins/dive/api/index.ts

ivette/src/frama-c/plugins/eva/api/general/index.ts

ivette/src/frama-c/plugins/eva/api/values/index.ts

ivette/src/frama-c/plugins/pivot/api/general/index.ts

ivette/src/frama-c/plugins/studia/api/studia/index.ts

ivette/src/frama-c/states.ts

src/plugins/api-generator/api_generator.ml

src/plugins/server/data.ml

src/plugins/server/package.ml

src/plugins/server/package.mli

src/plugins/server/server_doc.ml