add verbose option to build_task;

tuned;

build manager: manage directories/permissions, to minimize local administration;

read prefs properly;

allow explicit Isabelle rev in build task (e.g., for older Isabelle versions);

web app: proper document height;

merged

replace manual def. of timing function

add build manager module;

support ci job via hg_sync (cf. 7883f221d6d3);

tuned;

use Content-Digest header in HEAD requests instead of length (to track non-monotone changes);

merged

Simplification of sin, cos, exp of multiples of pi

minor performance tuning: more compact data;

removed unused/inefficient size_of_proof (see also 2241191a3c54);

tuned;

more robust: avoid crash of sleep() for negative time;

clarified signature;

clarified signature: more explicit types;

support "rsync --chmod --chown" via Rsync.Context;

tuned;

bash: proper bash_process via SSH; getenv: prefer light-weight ssh.execute;

clarified signature: support explicit cwd;

support bash via SSH;

clarified comments;

proper support for remote cwd;

clarified context for (remote) bash scripts: export variables are optional, support cwd;